Highly conjugated organic materials are currently the focus of great research activity, chiefly due to their interesting electronic and optoelectronic properties. They are being investigated for use in a variety of applications, including field effect transistors (FETs), thin-film transistors (TFTs), organic light-emitting diodes (OLEDs), electro-optic (EO) applications, as conductive materials, as two photon mixing materials, as organic semiconductors, and as non-linear optical (NLO) materials. Highly conjugated organic materials may find utility in devices such as radio frequency identification (RFID) tags, electroluminescent devices in flat panel displays, and in photovoltaic and sensor devices.
Materials such as pentacene, poly(thiophene), poly(thiophene-co-vinylene), poly(p-phenylene-co-vinylene) and oligo(3-hexylthiophene) have been intensively studied for use in various electronic and optoelectronic applications. More recently, fused thiophene compounds have been found to have advantageous properties. For example, bisdithieno[3,2-b:2′,3′-d]thiophene (1, j=2) has been found to efficiently π-stack in the solid state, to have a high mobility (up to 0.05 cm2/V·s), and to have a high on/off ratio (up to 108). Oligomers and polymers of fused thiophenes, such as oligo- or poly(thieno[3,2-b]thiophene (2) and oligo- or poly(dithieno[3,2-b:2′-3′-d]thiophene) (1)
have also been suggested for use in electronic and optoelectronic devices and have been shown to have acceptable conductivities and non-linear optical properties.
We have described some fused thiophene-based materials in U.S. Patent Application No. US2007/0161776 of He and in PCT Patent Application Publication No. WO 2006/031893 of He. A need for new fused thiophenes and methods for making fused thiophenes continues to exist, and the present invention is directed, in part, to addressing this need.